Aqueous (water-based) curable silicone release coating composition is well-known in this field.
For example, WO 2008019953 (Patent Reference 1, incorporated herein for reference) discloses a release coating composition comprising a polyorganosiloxane (A) having alkenyl groups, a crosslinking agent (B) having organohydrogensiloxane groups, a catalyst for the hydrosilylation reaction between (A) and (B), and an anchorage additive for enhancing the adhesion of the composition to a polymer film substrate, characterised in that the anchorage additive is the reaction product of a fluid polyorganosiloxane (C) containing at least one alkenyl group and at least one silanol group with a hydrolysable silane (D) containing at least one epoxide group.
For example, U.S. Pat. No. 5,672,428 (Patent Reference 2, incorporated herein for reference) discloses a silicone release polyester film coated with an aqueous silicone coating composition on one surface. The aqueous silicone release coating composition is made up of an alkylvinylpolysiloxane containing vinyl groups, a tin or platinum catalyst, a glycidoxysilane and an alkylhydrogenpolysiloxane. The glycidoxysilane is said to give excellent rub-off resistance performance.
For example, US 20030088042 (Patent Reference 3, incorporated herein for reference) discloses that release compositions of the invention comprise additives for improved anchorage of release coatings comprising the reaction product of: the reaction product of: 1) REhSi(ORA)3-h; 2) Rv1i Si(ORB)3-i; 3) a condensation catalyst; and 4) water, wherein RE=epoxide containing radical, Rv1=vinyl terminal olefinic monovalent hydrocarbon radicals, RA=hydrocarbon radicals; RB=hydrocarbon radicals; h=1-3, and i=1-3. The release coating compositions are said to have improved adhesion to paper and polymeric substrates.
For example, US 20040161618 (Patent Reference 4, incorporated herein for reference) discloses an additive for anchorage of release coating comprising (RaSiO(4-1)/2)n; n>3, a=1-3, R=an oxirane or epoxide comprising radical with at least one oxirane or epoxide and hydride being present on the molecule; or a carboxylic acid anhydride radical with at least one carboxylic acid anhydride and hydride being present on the molecule. The release coating compositions are said to have improved adhesion to paper and polymeric substrates.
For example, U.S. Pat. No. 6,410,134 (Patent Reference 5, incorporated herein for reference) discloses an aqueous silicone coating composition and polyester release films coated therewith. The aqueous silicone coating composition included an alkylvinylpolysiloxane, an alkylhydrogenpolysiloxane, a platinum complex catalyst and a water-soluble polyester resin is advantageously used for the preparation of a polyester release film having good release property and improved rub-off resistance.
Although water-based curable silicone release coating compositions are useful for low environmental burden and good in human safety without using flammable and harmful organic solvent, the above conventional water-based curable silicone release coating compositions have only insufficient rub-off resistance on the substrate and poor release property.
Because of relatively poor releasing property & rub-off resistance of cured layer, the above conventional water-based curable silicone release coating compositions can be used in limited applications. The above Patent References 1-5 fail don't always meet the desirable requirements on improved releasing property & rub-off resistance of cured layer. Particularly, WO 2008019953 discloses the similar unemulsified anchorage additive, but WO 2008019953 never teaches or suggests emulsifying the anchorage additive into water. Furthermore, it can be desired to emulsify silicone compound of said anchorage additive and other optional silicones (vinylsilicones, Si—H silicones, silicone resins, etc.) with specific nonionic surfactants with water-soluble polyvinylalcohol (PVA) or other co-surfactants. The above Patent References 1-5 are silent to use an emulsion of water-based anchorage additive as a component of a release coating composition. The applicant has surprisingly found that combined with water-based silicone-type anchorage additive, the potential application of water-based curable silicone release coating compositions will be broadened drastically.
Therefore, there still exists a need in the art for obtaining practically useful, safe and environmentally-friendly water-based curable silicone release coating compositions, and the production procedure of a cured release coating-bearing sheet-form substrate, i.e. coated release paper, PET film or other applications and allowing a high versatility of choice of components of the release coating composition.